Ginseng has been widely used from ancient times as the most typical nutritional tonic in some countries including Korea, China and other countries. Recently, the results of many studies on its components and pharmacological actions have been reported. The reported pharmacological actions of ginseng include central nervous system depression and excitation, protein and nucleic acid biosynthesis promotion, hematosis, liver function recovery, blood pressure lowering and elevation, arteriosclerosis prevention, blood glucose increase, anti-fatigue and anti-stress actions. In addition, ginseng was recently reported to have an AIDS virus growth inhibitory action, an anti-dioxin action and a sexual function improvement effect.
Generally, ginseng is used in the following three forms: raw ginseng (fresh ginseng) remaining intact without any processing after its harvest; white ginseng obtained by drying raw ginseng at ambient temperature; and red ginseng obtained by steaming and drying raw ginseng. Particularly, ginseng is used in the form of red ginseng because red ginseng shoes a higher pharmacological activity than that of raw ginseng or white ginseng.
Red ginseng is prepared according to the steps of: washing raw ginseng; steaming the washed ginseng at 90–100° C.; drying the steamed ginseng to a moisture content of 35–40 wt %; storing and aging the dried ginseng; drying the aged ginseng again to a moisture content of about 16 wt %; and trimming the dried ginseng. Compared with the raw ginseng, the red ginseng prepared as such shows an improvement in storage stability, a change in its components, and browning.
Particularly, during the step of steaming raw ginseng in the preparing process of red ginseng, the components of raw ginseng are chemically changed. For this reason, new components which are not found in raw ginseng or white ginseng are detected in red ginseng, and the amounts of other components which are originally contained in the raw ginseng also increased. Important components produced during the preparing process of red ginseng include saponin compounds, and non-saponin compounds such as polyacetylenes, acidic polysaccharides and amino acids. Of the non-saponin compounds, panaxytriol is a characteristic component found only in red ginseng. It is reported that red ginseng has higher saponin contents, about eight times higher acidic polysaccharide contents and about 25 times higher amino acid contents than those of white ginseng prepared from the same amount of raw ginseng.
Meanwhile, an extrusion process is an efficient and economic process as compared with other processes, because its unit operations, such as mixing, crushing, heating, molding and drying, are performed within a short time period. Since a material within an extruder undergoes not only shear force by the rotation of a screw but also pressure by the adjustment of a die exit, the extrusion process is a continuous process which involves physical force at high temperature and high pressure, particularly when applied to a heating process (Harper, Extrusion Cooking, pp 1–16, 1989).
From the 1930s, the extrusion process started to be regularly applied in industry as a solution in labor-intensive fields. A field in which the extrusion process had been first applied as a continuous process is a polymer plastic molding field, and recently, the extrusion process is applied in various industrial fields including food, feed, biological and medical products.
Since pasta was produced by a continuous process using a single-screw extruder in the middle 1930s, the extrusion process started to be systemically applied in the food industry (Harper, Extrusion of Foods, pp. 1–6, 1981). Application examples of the extrusion process in the food field include the puffed corn snack products, the pregellatinized starch, the texturization of vegetable protein, the pretreatment of fat extract, the sterilization, the conversion of polymeric biomaterials, and the conversion of residues in the preparation of bean-curds into intermediate products (RYU Gi-Hyung, Korean Society of soybean study 12(2): 43–48, 1995). However, there has been no case where the extrusion process was used for the processing of ginseng, particularly the preparation of red ginseng.